Preparation of chlorinated aromatic carboxylic acid esters



United States Patent BREBARATION 0F CHLORINATED- AROMATIC CARBOXYLIC ACID ESTERS' William I G; Tolamh San Rafael; (Calif; assignor to (Saliforniat Research Gorporation; San: Fianci'scm. (ialifr, a corporation of-Delaware N0 Drawing; ApplicationJuly 5,1955", Serial Nb; 520,096

6 Claim (0]..260-475) The present invention relates: to aproc'ess for.- the chlorination of aromatic carboxylic acid esters to produce the corresponding chloroalkyl ester of the aromatic acidby thedirect. chlorination of the alcohol portion of the'ester; e. g;, theformation ofchloromethyli benzoate from methyl benzoate, these chloroesters being, useful in the preparation of polyamides and polyesters employed intfibers, films-,,surface coatings, as selective chlorinating agents; and as materials from which aromatic acid chlorides." can. be produced by thermal rearrangement.

In, mycopending application Serial No. 498,116, filed March 30, 1955, there is disclosed a novel process: for the preparation of acid chlorides from aromatic carboxylic esters, e. g., terephthaloyl dichloride .from-dimethyl terephthalate, by passing chlorine into the esterat anelevated temperature withiirabout thexrange.of.30.0:" F. to 700"F..

Now in accordance with. the present: invention; L have found" that. chlorinating' the. esters. at: lower temperatures, that is, at temperatures within azrange'having: an.- upper limit below about 300 R, selective chlorination of; the alkyl group of. the alcohol'portionof.the:esten occur-stand resultsinhigh. yields of the chloroalkyl ester. Int generalgthe over-'all-reacti'on: maybe illustratedibyj the'following equations indicating the reactions. occurring; during chlorination of methyl benzoate pursuant: to the invention:

As shown, the alkyl group of the" ester canbe chlorinated in varying degrees depending on theamount of chlorine employed and time of reaction in accordance with regular rules of stoichiometry;

The reaction can becarriedout with or' without catalyst, e. g., light, and with or without solvent, e; g'-., carbon tetrachloride. As indicated, temperatures below about 300 F. are suitable, temperaturesin' the range 0-300 F. are operable and temperatures of the order'of room temperature; that is, around 75 F1, have been found satisfactory and are generally employed. Rcactiom times can vary from less than 1 hour to 3 hours, usu-al reaction" times being-ofthe orderof l /2 lioursa- A suitable aromatic carb'oxylic aci'd ester-can: be=v defined as one obtained by esterification of an aromatic carboxylic acid being free of chlorinereactive-s-ubstituen-t groups on the ring. or. aromatic. nucleus, e. g., alkyl groups: The aromatic carboxylic acidmoreover. camcontain a single aromatic nucleus or two or more fused or unfused aromatic nuclei. Examples of suitable acids are benz-oic, orthophthalic, isophthalic and terephthalic acids, chlorobenzoic, naphthoic, diphenic acid, and trimesic acids.

2,816,134 Patented Dec. 10, 1957 'ice carbons being most advantageously employed. Specific examples of suitablealcoholsare methanol, ethanol, propanol, isopropanol, butanol, amyl alcohol, ethylene glycol, propylene glycol; glycerol, diethylene-glycol; The aliphatiealcohols employed in the preparation of the ester may have one or more hydrogen atQmsoftheir alkyl radicals replaced by aromatic nuclei.v For example, benzyl alcohol, benzyl carbinol and the like may be employed.

Thereaction is conveniently carried'out'in suitable-apparatus such as a turbomixer, equippedwith gas inlet, vapor condenser and exit lines for the-withdrawal of hydrogen chloride and chlorinev recovery; In carrying out the: reaction the aromatic carboxylicv acid ester is heated to thezdesiredtemperature and while stirring the chlorine ispassedithereinto. Upon completion of thedesired'de greeoftreaction as indicated by the amount of chlorine uptake and the amount of. hydrogen chloride evolution, the contents are withdrawn from the turbomixer and fractionated to recover the chlorinated ester.

The following examples are given to-illustrate the'practice'ofthe invention:

Example].

A vertical glass tube, fitted with a sint'ere d' glass disk at' itsbase through which, chlorine couldbe introduced and" with a condenser at the top to permitflreflux of reactants andfrom whichoit-gases could be vented. was immersed in an oil bath, charged with 40.9 grams, of

methyl benzoate, heated'up to 300'F;, and chlorine inretical. 20.8

Example 2 small turbomixer was charged with 14657 grams of methyhbenzoate:and'three 100 watt light bulbsarranged uniformly around and adjacent to the liquid in the turbomixer; Agitationwas-begun and-chlorine introduced at arateof 1.08 grams per minute-over a period'ofi 5 hours at a temperature of F. A total of 324 gramsof chlorine was introduced and 117 grams recovered. Titrat'ion of thewater scrubberfor theexit gases showed: the

'presenceofl.25.moles-of. acid, largely hydrochloric; The

li'quidproducts from. the turbomixer weighed-i279t6.g-rams. This indicates the substitution of. approximately 3.85 equivalents of chlorineper. mole'of: methyl benzoate. A

sample. oi. this. product was saponifiedtwithaqueous caustic. Upon acidification of the caustic soluble. products, a precipitate was formed which, when filtered, Washed, and dried, was identified aschlorobenzoic acid, neutral eqpivalent-.1 53.6 (theoretical 15615) This-indicatedthat some ring chlorination occurred during this reaction. Qhlorine analysis of thecrude productsshowcdzthe presence, of. 48.27% chlorine, indicating. the. methyl. group: to

have been completely chlorinated.

Example 3 A turbomixer was charged with 150.2 grams of ethyl benzoate and the vessel illuminated by three watt light bulbs placed outside of and adjacent to the vessel walls. Chlorine was introduced at a rate of 1.1 grams per mim ucts was distilled under 10 mm. Hg pressure, and were shown to contain 58.8 grams of unreacted ethyl benzoate and 52.3 grams of chlorinated esters.

The other half of the products were heated at atmospheric pressure in a distillation zone to convert them to the acid chloride. The following fractions were removed overhead from the distillation zone:

Analysis of the above data showed there had been produced 53.8 grams of benzoyl chloride and 0.24 mole total aldehydes by the thermal decomposition of the chlorinated products. This proves that the product of this chlorination reaction contained no chlorine on the aromatic ring but rather on the ethyl group.

Example 4 Isopropyl benzoate (164.2 grams) was charged to a turbomixer which was illuminated by three 100 watt light bulbs placed just outside the reactor. The temperature was raised to 150 F. and chlorine introduced at a rate of 0.4 gram per minute over a period of 2 hours. A total of 47.8 grams of chlorine was introduced and 0.6 gram. recovered. A total of 0.54 mole of acid was recovered from the vent gases by the water scrubber. The products from the turbomixer weighed 180.2 grams and had an acid number of 341. On the basis of this acid number, the product contained 60.7% of monochloroester.

By a procedure similar to that used in earlier examples the products were shown to contain the following constituents:

Moles Unreacted isopropyl benzoate 0.393 ot-ChlOIOCStBI' 0.37 ,B-Chloroester 0.183 B-Polychloroester 0.030

This accounts for 97.6% of the products.

If the crude products are heated at atmospheric pressure benzoyl chloride is produced.

Example 5 perature climbed to 290 F. A total of 49 grams of chlorine was passed and 0.6 gram recovered. A total of 0.775 mole of acidity was .found in the vent gases. The turbomixer products, weighing 235.6 grams, had an acid number of 371. On this basis, they contain 81.7% of chloroester, most of which was material in which the methylene group of the ester was chlorinated.

Example 6 A turbomixer, illuminated by three watt light bulbs, was charged with 200 grams of dimethylterephthalate and the temperature raised to 260 F. and chlorine introduced at a rate of 0.95 gram per minute over a period of 1.75 hours. A total of 101 grams of chlorine was introduced and 3.1 grams recovered. The organic products weighed 15 245.5 grams and had an acid number of 815. Th1s cor- Pot vapor responds to 95.7% of monochloroester. Temper- Temper- VOL, Wt., g. Cut Ide ty One half of the products was d1st11led at 5 mm. Hg presature, C. ature, m1. N o.

sure to obtain the following fractions:

203 53 0 20 Pot Vapor Evolution of noncon- Temper- Temperml. g. Run Identity densible gas, odor of v ature, O. ature,0. No. 80 4.0 3 9 1 acetaldehyde. Iden- 3. 5 3 6 2 tified chloral and tri- 197 3.5 3 6 3 chloroacetyl chloride; Some decomposition occurothercompoundsalso 76 25 0 0 ring in the pot. Neutral present. 25 6 25 0 0 equivalent of pot products 202 15.0 a 17.1 4 now 67.6, saponiflcation 207 25.0 27. 4 5 equivalent 63.4.

210 6. 5 6. 7 6 188 6.0 5. 6 1 N. E.=71.1, S. E. =75.3.

320 233 6.0 5. 5 7 200 9.0 12. 8 2 N. E.=75.6, S. E.=74.55, per- 'B0tt0ms. 10.3 cent chlorine 10.4, 10.5.

Distillation column re- 3 N 4 5 d 6 b d 1 1 30 9o 23 a N E 7 0 S I 3 $2 3 uts 05, an 1' 193 1 18.0 .1

We 6 com an had a c 300 240 42.5 56.1 4 N. E.=64.0, s. E.=61.5, percontent of 12.23% and a neutral equivalent of 97.0. Cut cent 01:22.35, 2149, No. 7, percent chlorine 7.68, 7.74; neutral equivalent 85.2. Bottoms" 8 1 N.E.=neutral equivalent. 1 S.E.=saponifieation equivalent.

From these results it was calculated that the original crude product had contained 0.266 mole of monochloroester, 0.511 mole of dichloroester, and a trace of polychloroesters. These materials can be converted by heating to the acid chloride.

Obviously many modifications and variations of the in vention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. Process for the preparation of a chlorinated aromatic carboxylic acid ester, which comprises contacting an aromatic carboxylic acid ester with chlorine at a temperature above about 0 F. but below about 300 F. for a period of time suificient to chlorinate the alcohol portion of the ester.

2. Process according to claim 1 wherein the ester is derived from an alcohol having 1 to 8 carbon atoms in the molecule.

3. Process according to claim 1 wherein the ester is derived from an aromatic carboxylic acid having a single aromatic nucleus.

4. Process according to claim 3 wherein the ester is derived from an alcohol having 1 to 8 carbon atoms in the molecule.

5. Process according to claim 4 wherein the ester is 'derived from an alcohol of 1 to 3 carbon atoms in the molecule.

6. Process according to claim 5 wherein the ester is derived from benzene carboxylic acids.

References Cited in the file of this patent UNITED STATES PATENTS 1,866,849 George July 12, 1932 

1. PROCESS FOR THE PREPARATION OF A CHLORINATED AROMATIC CARBOXYLIC ACID ESTER, WHICH COMPRISES CONTACTING AN AROMATIC CARBOXYLIC ACID ESTER WITH CHLORINE AT A TEMPERATURE ABOVE ABOUT 0*F. BUT BELOW ABOUT 300*F. FOR A PERIOD OF TIME SUFFICIENT TO CHLORINATE THE ALCOHOL PORTION OF THE ESTER. 